docs: def dataframe(self):
          """
          Returns a pandas DataFrame where each row is a representation of the
          Game class. Rows are indexed by the boxscore string.
          """
          frames = []
          for game in self.__iter__():
              df = game.dataframe
              if df is not None:
                  frames.append(df)
          if frames == []:
              return None
          return pd.concat(frames)